5901 23RD DR W Geotech Report 2025-07-29

I October 22,2007 Project No.T-5922-1 5.10 Pavements Pavement subgrades should be prepared as described in Section 5.2 of this report. Regardless of the relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade should be proofrolled with heavy construction equipment to verify this condition. The thickness of the various components of the pavement depends not only on the subgrade soils, but also the traffic loading conditions to which the pavement will be subjected. For design, we have assumed the traffic loading can be represented by design 18-kip equivalent single axle loads (ESALs) of 50,000 for light traffic and 500,000 for heavy traffic areas. These ESALs represent traffic loading equivalent to 4 and 24, loaded (80,000 pound gross vehicle weight) tractor-trailer rigs, respectively, traversing the pavement per day over a 20-year design life. If heavier traffic loading or volumes are expected, we should reevaluate the following recommended pavement sections. Light Traffic: • Two inches of hot mix asphalt (HMA) over four inches of crushed rock base (CRB) or three inches of asphalt-treated base(ATB) Heavy Traffic: • Three inches of HMA over six inches of CRB or four inches of ATB The paving materials used should conform to the current Washington State Department of Transportation (WSDOT)specifications for 1/2-inch hot mix asphalt(HMA)surfacing,CRB, and ATB. Long-term pavement performance will depend on surface drainage. A poorly-drained pavement section will be subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their supporting capability. To improve pavement performance, we recommend surface drainage gradients of at least two percent. Some longitudinal and transverse cracking of the pavement surface should be expected over time. Regular maintenance should be planned to seal cracks when they occur. 6.0 ADDITIONAL SERVICES Terra Associates, Inc. should review final designs and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and implemented into project design. We should also provide geotechnical services during construction in order to observe compliance with the design concepts, specifications, and recommendations. This will allow for design changes if subsurface conditions differ from those anticipated prior to the start of construction. 7.0 LIMITATIONS • This report is the property of Terra Associates, Inc. and was prepared in accordance with generally accepted geotechnical engineering practices. This report is intended for specific application to the Seaway Center Lot 3C project in Everett, Washington and for the exclusive use of PacLand and their authorized representatives. No other warranty,expressed or implied, is made. I Page No. 12 I